NAME

       io_getevents - read asynchronous I/O events from the completion queue

LIBRARY

       Standard C library (libc, -lc)

       Alternatively, Asynchronous I/O library (libaio, -laio); see VERSIONS.

SYNOPSIS

       #include <linux/aio_abi.h>    /* Definition of *io_* types */
       #include <sys/syscall.h>      /* Definition of SYS_* constants */
       #include <unistd.h>

       int syscall(SYS_io_getevents, aio_context_t ctx_id,
                   long min_nr, long nr, struct io_event *events,
                   struct timespec *timeout);

       Note: glibc provides no wrapper for io_getevents(), necessitating the use of syscall(2).

DESCRIPTION

       Note:  this  page  describes  the  raw  Linux system call interface.  The wrapper function
       provided by libaio uses a different type for the ctx_id argument.  See VERSIONS.

       The io_getevents() system call attempts to read at least min_nr events and up to nr events
       from the completion queue of the AIO context specified by ctx_id.

       The  timeout argument specifies the amount of time to wait for events, and is specified as
       a relative timeout in a timespec(3) structure.

       The specified time will be rounded up to the system clock granularity  and  is  guaranteed
       not to expire early.

       Specifying timeout as NULL means block indefinitely until at least min_nr events have been
       obtained.

RETURN VALUE

       On success, io_getevents() returns the number of events read.  This may be 0, or  a  value
       less  than  min_nr,  if  the  timeout  expired.   It may also be a nonzero value less than
       min_nr, if the call was interrupted by a signal handler.

       For the failure return, see VERSIONS.

ERRORS

       EFAULT Either events or timeout is an invalid pointer.

       EINTR  Interrupted by a signal handler; see signal(7).

       EINVAL ctx_id is invalid.  min_nr is out of range or nr is out of range.

       ENOSYS io_getevents() is not implemented on this architecture.

VERSIONS

       You probably want to use the io_getevents() wrapper function provided by libaio.

       Note that the libaio wrapper function uses a different type (io_context_t) for the  ctx_id
       argument.   Note  also  that  the  libaio  wrapper  does  not  follow  the usual C library
       conventions for indicating errors: on  error  it  returns  a  negated  error  number  (the
       negative  of  one  of  the  values  listed  in ERRORS).  If the system call is invoked via
       syscall(2), then the return value follows the usual conventions for indicating  an  error:
       -1, with errno set to a (positive) value that indicates the error.

STANDARDS

       Linux.

HISTORY

       Linux 2.5.

BUGS

       An invalid ctx_id may cause a segmentation fault instead of generating the error EINVAL.

SEE ALSO

       io_cancel(2), io_destroy(2), io_setup(2), io_submit(2), timespec(3), aio(7), time(7)